Air sampling is used to quantify and qualify the contents of an environment. Laboratory analyses of the samples provide critical information relative to the potential exposure to harmful agents. Bioaerosol sampling focuses these processes on particles of biological origin. These agents include, but are not limited to, viable and non-viable fungal spores, bacteria, pollen, skin cells, fibers and insect parts.
The 25-millimeter (mm) cassette equipment with a 0.8 micron methylcellulose ester (MCE) filters are routinely used in the practice of industrial hygiene. More specifically, these cassettes are commonly used in the evaluation of airborne concentrations of asbestos. Bioaerosol agents can be recovered with the standard use of these cassettes, however; problems exist with regard to analyses of data collected by standard methodologies. Bioaerosol components are usually in far less airborne concentrations when compared to asbestos related industrial hygiene and/or abatement projects. Therefore, it becomes necessary to sample greater volumes of air in order to achieve appropriate detectable levels of bioaerosols using MCE filter technology. Airflow turbulence occur if 0.8-micron methylcellulose ester filters are exposed to air velocities over 15 liters per minute (L/m) that result in non-uniform particle distribution. Therefore, the rate of airflow cannot be adjusted over 15 L/m without potential damage to the MCE filter. Therefore, sample time is the only parameter available for manipulation. Under normal conditions, several hours of sampling are required in order to obtained an appropriate volume of air for bioaerosol analyses. These time constraints are problematic, especially when considering the costs related to on-site technical man-hours and/or the need for additional equipment for each individual sample location. The MBI Vortex Bioaerosol Cassette Insert has the unique ability to reduce sampling time to minutes without damaging MCE filters and thereby creating a highly efficient and effective bioaerosols recovery unit.
The MBI Vortex Bioaerosol Cassette Insert is designed for a specific niche in the marketplace. Until recently, bioaerosol sampling has been performed using two basic types of collection methodologies; filtration and impact. Filtration methodologies utilize filter cassettes that are equipped with filters having a variety of design, components, and pore sizes. Typically most fungal bioaerosol components are above 1 micron in size. Hence, filters having a pore size just below 1 micron are useful in the filtration of fungal bioparticulate from the air without excessive air resistance. After collection, filters can be prepared for culture and/or viewed microscopically. The use of filters for fungal culture has proven to be inefficient with regard to recovery and is typically not recommended. Direct observation under microscope is possible, however; typically the sampling time required to collect detectable amounts rendered this sampling technique as implausible. Impacting methods have emerged as the principle means to evaluate airborne fungal bioparticulate. Impacting occurs directly onto agar-media surfaces for culture or on to special fixatives for direct microscopic examination. While some benefits exist with respect to culture recovery, the overall processes inherently introduces a bias of recovery and generally requires at least 5-7 days for incubation prior to analyses. Impacting directly on to special fixatives does allow the potential for an immediate analysis, however; some limits exist with regard to identification and classification.
Regardless, impaction methods remain vulnerable to a variety of parameters that effect xe2x80x9crecovery efficiencyxe2x80x9d. These factors include airflow, particle size, aerodynamics, etc . . . No impacting sampler is 100% efficient. Therefore, some percentage bioparticulate merely passes through the sampler and remains undetected.
Filtration technologies vastly improve recovery efficiency. The selection of filter pore sizes that are below the dimensions of fungal particulate ensures retention. Culture from filters have demonstrate relatively low recovery and are not generally recommended for air sampling, however; direct microscopic examination of filters offers an improved recovery efficiency over traditional impacting methods. In the past, direct filter examination has proven impractical because of the time required to collect samples, desiccation of recovered spores, as well as, increased man-hour and equipment costs. However, the MBI Vortex Bioaerosol Cassette Insert represents a new design that concentrates fungal bioparticulate into a distinct zone on the receiving filter. The concentration of recovered agents in effect reduces the collection area of the MCE filter thus allowing a reduction in sampling time without compromising detection levels or filter integrity. The MBI Vortex Bioaerosol Cassette Insert capitalizes on standard and accepted sampling methodologies, but now expands the use of 0.8 micron MCE filtration collection methodology into the field of fungal and other bioaerosol identification and reporting.